> Many contracts that have illegal/unenforceable clauses have been run by lawyers...
Many contracts that have illegal/unenforceable clauses have them because they have been been run by lawyers. They know perfectly well that most ordinary people are in no position to tell whether or not a clause is enforceable.
My landlady when I was at uni (74-77) tried it on me not realizing that my girlfriend was studying land law and contract law at the time.